1. Field of the Invention
The invention relates to a microphone, more specifically to a microphone with an improved diaphragm that increases the sensitivity and responsiveness of the microphone.
2. Description of the Related Art
Microphones can be divided into several categories depending on the transducer principle used. The dynamic microphone is a popular conventional microphone and comprises a magnet which has opposite poles and which is mounted inside a housing, a voice coil which is disposed movably in a magnetic field between the opposite poles of the magnet, and a diaphragm which is attached to the upper end of the voice coil and which is spread over the cross section of the housing.
In the dynamic microphone, the compression and rarefaction of sound waves actuate the diaphragm, thus causing movements in the attached voice coil and creating a varying magnetic flux. This varying flux, together with the magnetic field generated by the magnet, produces electrical signals which are provided to an amplifier and then to a speaker.
FIG. 1 shows a light and flexible conventional diaphragm 10 that comprises a central convex portion 11, an annular convex portion 12 encircling the central convex portion 11, the juncture of the convex portions 11, 12 being attached to a voice coil 13 located below, a plurality of ribs 14 on the surface of the annular convex portion 12, and a flat periphery 15. Different portions of the diaphragm 10 respond to different frequency ranges. The central convex portion 11 responds to a high frequency range, the ribs 14 respond to a mid-frequency range, and the annular convex portion 12 responds to a low frequency range. The quality of the broadcast sound depends upon the flexibility and lightness of the components. In a high quality microphone, the high frequency range responding component is rigid and light, while the low frequency range responding component is flexible. However, all of the components of the conventional diaphragm 10 are made of the same material. They all have the same thickness and rigidity. Thus, a microphone which uses the diaphragm 10 is unable to deliver high quality sounds.
Another type of conventional diaphragm 20, as shown in FIG. 2, comprises a flat periphery 213, an annular convex portion 212, a central convex portion 211, and a membrane 22 of equivalent size as the central convex portion 211 and covering the central convex portion 211. The addition of the membrane 22 increases the rigidity required in the high frequency range. However, the membrane 22 is attached back-to-back with the central convex portion 211 by an adhesive. Such adhering method increases the weight of the diaphragm 20, thereby resulting in an adverse effect on the sound quality.